code: def test_get_default_mesh(self):
      self.assertIsNone(api.get_default_mesh())
      with api.default_mesh(self.mesh):
          self.assertEqual(api.get_default_mesh(), self.mesh)
  
          with api.default_mesh(self.mesh.host_mesh()):
              self.assertEqual(
                  api.get_default_mesh(), self.mesh.host_mesh()
              )
  
          self.assertEqual(api.get_default_mesh(), self.mesh)
  
      self.assertIsNone(api.get_default_mesh())
  
imports: from absl.testing import parameterized
  import numpy
  from tensorflow.dtensor.python import api
  from tensorflow.dtensor.python import d_random
  from tensorflow.dtensor.python import layout
  from tensorflow.dtensor.python import numpy_util
  from tensorflow.dtensor.python.tests import test_util
  from tensorflow.python.eager.polymorphic_function import polymorphic_function
  from tensorflow.python.framework import constant_op
  from tensorflow.python.framework import dtypes
  from tensorflow.python.framework import errors_impl
  from tensorflow.python.framework import ops
  from tensorflow.python.ops import array_ops
  from tensorflow.python.ops import nn_ops
  from tensorflow.python.ops import stateless_random_ops
  from tensorflow.python.platform import test
label_desc: Use image node_id 11 for calling the APITest obj's underlying member method code with example usage: obj.test_get_default_mesh() without return types